Water-proof coaxial cable with readily separable layer



April 27, 1965 s. w. TRILL 3,180,926

WATER-PROOF COAXIAL CABLE WITH READILY SEPARABLE LAYER Filed Dec. 28,1961 CDPPER WIRE pomsoaurmwe L f HYENE oLggl'flgfNfeb Y 7 MIN L LERPDLYETHYLENE BRAIDED WIRE 5 CARBON eLAcIM ANTIOXIDANT INVENTOR.

SIDNEY W. TRILL United dtates Patent 3,180,926 WATER-PRUQF C(UAXIALCABLE 'l JilTll READZLY SEPARAELE LAYER Sidney W. Trill, carsdale, NEL,assigncr to Phelps Hodge Copper Products (Importation, New Yorlr, FLY acorporation of Delaware Filed Dec. 28, 1961, Ser. No. 162,773 Claims.(6!. l74=ld7) The present invention relates to electrical cable and moreparticularly to an improved coaxial cable.

it is desirable that coaxial cable laid under water or under wet groundresist longitudinal movement of water through the cable. It is alsodesirable that layers of a coaxial cable be readily separable to connecttheir conductors to other cables, to junction boxes, or for testing ofthe cable. At the present time coaxial cables are'not particularly welladapted to withstand longitudinal water pressure, norare theyparticularly well adapted to have their layers readily separable forsplicing.

It is an objective of the present invention to provide a coaxial cablein which the insulation around the outer conductor is easily extrudableand, after extrusion, readily separable from the remainder of the cable.it is a further objective that the insulation adjacent the outerconductor provide protection against longitudinal passage of Inaccordance with the present invention, a coaxial cable is provided inwhich a filled compound of a mixture of polyethylene, polyisobutyleneand a mineral filler, preferably powdered acid magnesium metasilicate,is extruded over or under or within the spaces of the braided outerconductor of the coaxial cable. The filler renders the dielectricalmaterial about the braid less cohesive and enables the outer conductorto be readily separated from the other portions of the cable. The fillerselected for this purpose should be non-hygroscopic and unsusceptible tofungus and should not increase the electrical attenuation or otherwisealter the electrical characteristics of the cable.

Other features of the present invention will be apparent from the belowdetailed description of a preferred embodiment, taken in conjunctionwith the accompanying drawing in which the single figure is a sideelevational view showing a coaxial cable embodying the presentinvention.

In the drawing, the coaxial cable comprises an inner electricalconductor 1, generally of copper wire. The inner conductor 1 issurrounded by a layer 2 of electrically insulative material, preferablypolyethylene which is extruded over conductor 1. An outer conductor 3,preferably of braided copper wire, surrounds the insulative layer 2. Acovering layer 4 of a mixture of mineral filler, polyisobutylene andpolyethylene surrounds the outer Patented Apr. 27, 1965 conductor 3 andis preferably extruded onto conductor 3. Talc (powdered acid magnesiummetasilicate) is the preferred mineral filler although diatomaceousearth, whiting (calcium carbonate), silica (silica dioxide), or hard orsoft clays (mixtures containing hydrous aluminous minerals) may be used.A preferred mixture for layer 4 is polyethylene, polyisobutylene andtale, in equal proportions by weight.

A weather protective layer 5, preferably of extruded polyethylenecontaining carbon black and an antioxidant, covers layer 4.

Although the above description and the drawing relate to the use of thefilled polyethylene-polyisobutylene material on the outside of the outerconductor, it is often desirable that the filledpolyethylene-polyisobutylene material be applied underneath, over, andWithin the interstices of the braided outer conductor 3.

Modifications may be made in the present invention within the scope ofthe subjoined claims.

I claim:

1. In a coaxial cable, the combination of an inner conductor, aninsulative layer around the inner conductor, an outer conductor ofbraided wire around the insulative layer, and about the outer conductor,an extruded layer consisting essentially of a mixture of polyethylene,polyisobutylene and suflicient mineral filler to render the extrudedlayer relatively non-cohesive with the outer conductor so that the outerconductor and the extruded layer are readily separable.

2. The combination defined in claim 1, in which the mixture is composedof substantially equal proportions by volume of polyethylene,polyisobutylene and the mineral filler.

3. The combination defined in claim 1, in which said extruded layersubstantially fills the interstices of the braid.

4. The combination defined in claim 1, in which the mineral filler ispowdered acid magnesium rnetasilicatc.

5. The combination defined in claim 1, in which the mineral filler iswhiting.

JOHN F. BURNS, Primary Examiner. JOHN P. WILDMAN, LARAMIE E. ASKlN,

Examiners.

1. IN A COAXIAL CABLE, THE COMBINATION OF AN INNER CONDUCTOR, ANINSULATIVE LAYER AROUND THE NNER CONDUCTOR, AN OUTER CONDUCTOR OFBRAIDED WIRE AROUND THE INSULATIVE LAYER, AND ABOUT THE OUTER CONDUCTOR,AND EXTRUDED LAYER CONSISTING ESSENTIALLY OF A MIXTURE OF POLYETHYLENE,POLYISOBUYLENE AND SUFFICIENT MINERAL FILLER TO RENDER THE EXTRUDEDLAYER RELATIVELY NON-COHEXIVE WITH THE OUTER CONDUCTOR SO THAT THE OUTERCONDUCTOR AND THE EXTRUDED LAYER ARE READILY SEPARABLE.